Recently, the use of immunosuppressants in ophthalmic clinics is increasing because of increased corneal transplantation and autoimmune disease, and new drugs are actively being developed to reduce adverse effects of the immunosuppressants. Immunosuppressants for ophthalmic diseases are generally formulated as eye drop preparations. Since currently used drugs do not penetrate the cornea well, they must be used in large quantities, which results in adverse effects. The cornea is permeable to amphiphilic drugs containing hydrophilic and lipophilic moieties.
Corneal transplantation is a surgical procedure in which a damaged or diseased cornea of a patient is replaced with a donor cornea to restore vision. With advances in corneal preservation methods, surgical techniques and surgical devices as well as inhibition of corneal transplant rejection, corneal transplantation has become the most frequently performed transplantation surgery globally. Since corneas remain transplant viable even after cardiopulmonary function has stopped, it is more successful than other organs and is the only actively performed organ transplantation in Korea where brain death is not legally accepted. According to the Korean Network for Organ Sharing, the number of corneal transplants performed each year is on the rise, with 405 corneal transplants being performed in 2007. In the US, well over 40,000 corneal transplants have been performed in the period between 1990 and 2007.
As corneal transplantation has become increasingly common, several problems have arisen and efforts are underway to negate such problems. Corneal transplant rejection is an immune-mediated inflammatory response and accounts for the majority of corneal transplant failure. Steroids have been used to reduce corneal transplant rejection. However, long-term use of steroids may result in increased intraocular pressure, delayed wound healing, complications such as cataracts and even high doses cannot stop rejection in certain high-risk individuals. Recently, efforts are underway to reduce rejection using immunosuppressants rather than steroids. It has been reported that, in groups at high-risk of corneal transplant rejection, those treated with the immunosuppressant cyclosporin A showed less rejection than those treated with steroids alone. In an animal model, a group treated with FK506 (tacrolimus) after corneal xenotransplantation was reported to show less inflammatory cell infiltration as compared to the untreated group. Although the use of FK506 or cyclosporin A in patients who have received organ transplants provides excellent immunosuppressive effects, adverse effects of the drugs such as the risk of nephrotoxicity, hypertension, metabolic disorders, diabetes, etc. are problems.
Autoimmune diseases occur when the body launches an immune system attack against its own tissues. Although it is thought that autoimmune diseases are associated with overactive or improper control of immune response induced by the change in the environment of cytokines (signaling molecules that control and stimulate the body's defense system) in the body against viruses or bacteria, its exact cause is not known. It is believed that environmental, genetic and immunological factors are involved. At present, more than 80 autoimmune diseases are known. According to a study in the US, the number of rheumatoid arthritis patients is 2.1 million, the number of fibromyalgia patients is 3.7 million, the number of psoriasis patients is 4-4.5 million, 10-30% of those also suffering from arthritic, the number of leukoplakia patients is 4 million, and the number of Sjogren syndrome patients is 2-3 million. Well-known autoimmune ophthalmic diseases include uveitis, Behcet's disease and keratoconjunctivitis. Recently, as xerophthalmia is identified as an immune-mediated inflammatory disease, it is also regarded as an autoimmune disease. Uveitis is a representative autoimmune ophthalmic disease. The uvea, which consists of the iris, the ciliary body and the choroid, is subject to inflammation because it is rich in blood vessels and connective tissues. Uveitis refers to inflammation of the uvea. At present, the cause of this disease is not certain, syphilis and tuberculosis being known as risk factors. Immune system abnormalities are suspected to be the cause of uveitis. Although inflammation of the uvea can also be caused by bacteria or viruses, it is classified as an autoimmune disease since there are many immunological inflammatory responses. Topical or systemic steroids have been used for treatment of uveitis. However, treatment with topical (e.g. eye drop) or systemic steroids requires high doses if the drug does not sufficiently reach the uveal tissue. In this case, severe adverse effect may occur. In patients who do not respond to steroid therapy or those who cannot endure the adverse effects of systemic steroids, immunosuppressants are used. However, even in this case, the treatment is often interrupted due to adverse effects such as bone marrow suppression, hemorrhagic cystitis, nephropathy, etc. As a result, patients frequently go blind. Accordingly, development of an eye drop for treatment of ophthalmic diseases transducing well into the eyes and having fewer adverse effects is needed.
Xerophthalmia (eye dryness) is a medical condition in which the eye fails to produce enough tears or the tear film becomes unstable due to excessive evaporation, causing foreign body sensation or irritation. That is to say, xerophthalmia occurs when secretion of tears is reduced or is accompanied by diseases of the eyeball and accessory organs, such as disorder or inflammation of the eyelid, skin diseases (e.g., Stevens-Johnson syndrome or pemphigoid), or systemic diseases (e.g., vitamin A deficiency or Sjogren syndrome) (Ophthalmology, 7th ed., Dong-Ho Yoon, Sang-Wook Lee, Ouk Choi, Ilchokak, 2005). According to a recent survey conducted by Chung-Ang University Hospital, 75% of Korean adults suffer from eye dryness, one out of three of those cases involving serious inflammation of the cornea.
For treatment of xerophthalmia, focus has made on supplementing artificial tears in the form of eye drops, or transiently or permanently blocking the lacrimal canals to keep the tears above a certain level. Recently, as xerophthalmia is newly recognized as an inflammatory disease, anti-inflammatory therapy for xerophthalmia is being investigated, and improvement of symptoms is reported in patients with severe eye dryness.
As the inflammatory changes of the ocular surface in xerophthalmia, including increased T lymphocytes, increased level of various inflammatory mediators including cytokines, or the like, are proven, suppression of inflammation on the ocular surface has become a main concern of xerophthalmia treatment. Cyclosporin A 0.05% eye drops (Restasis™) are one of such drugs. However, cyclosporin A frequently has adverse effects in xerophthalmia patients. The most common adverse reaction is a burning sensation of the eyes, and it is reported that 1-5% of patients suffer conjunctival hyperemia, secretion, epiphora, pain in the eyes, foreign body sensation, itching, stinging, vision disorder (often blurred vision), etc. Accordingly, development of new anti-inflammatory and immunosuppressant drugs with fewer adverse effects is needed.
Although use of immunosuppressants for ophthalmic diseases is increasing gradually, use thereof is restricted due to severe adverse effects. An immunosuppressant refers to any substance used to suppress the ability of the body to produce antibodies (humoral immunity) or to reduce or interrupt cell-mediated immunity. It is mainly used for treatment of autoimmune diseases, selective immunosuppression, e.g., in hemolytic diseases of newborns, and prevention of rejection after organ transplantation. Use of immunosuppressants is restricted because of adverse effects such as anemia, leukopenia, thrombocytopenia, hair loss, and so forth. Secondary metabolites from bacteria and fungi were developed as immunosuppressive agents with less cytotoxicity. Cyclosporin A and FK506 are typical examples widely used for organ transplant patients, but they still have adverse effects.
For treatment of ophthalmic diseases, change of the preparation form from a systemic one to an eye drop is required to reduce adverse effects of existing drugs. Recently frequently used immunosuppressants including cyclosporin and FK506 are used for systemic purposes. However, since both drugs may damage the kidneys and nerves, development of eye drop preparations is being carried out in order to reduce adverse effects while enhancing medicinal effects. It was reported that administration of FK506 as an eye drop preparation provides an excellent effect of delaying rejection after corneal transplantation. Further, it was reported that administration of FK506 as an eye drop preparation to xerophthalmia patients achieved better results than common eye dryness drugs. According to a report by the Department of Ophthalmology, Catholic University of Korea, administration of cyclosporin-containing eye drops to xerophthalmia patients for 3 months resulted in increased secretion of tears. Especially, the effect was better in those who had xerophthalmia accompanied by systemic diseases. However, this result is restricted in that the period of clinical testing was too short. A research team from the University of Pennsylvania School of Medicine reported in the Journal of the American Medical Association that administration of cyclosporin-containing eye drops was very effective for treatment of eye dryness in patients with moderate-to-severe xerophthalmia, which occur in 15-34% of the elderly.
Although the eye drop preparation is much more effective than that for systemic administration and is capable of minimizing adverse effects, introduction of a new technique is required since it is very difficult for the drug to penetrate into the eyes. Especially, protein drugs are much more difficult to deliver into the eyes. The delivery of the drug through the cornea is disturbed by many factors, including differences in the chemical compositions of the epithelium and stroma of the cornea. Whereas the corneal epithelium is rich in lipids and is more permeable to undissociable drugs, the corneal stroma passes only dissociable ones. In addition, the corneal endothelium, which is rich in lipoids, passes only lipophilic substances. Thus, the cornea tends to be permeable to amphiphilic drugs which have both lipophilic and hydrophilic moieties. For this reason, an excessive amount has to be administered if the associated drug cannot penetrate the cornea well, which may cause adverse effects.
Korean Patent No. 472938 relates to a transport domain-target protein-transport domain fusion protein with advanced cell-transducing efficiency and uses thereof. There is disclosed an advanced cell-transducing fusion protein in which a protein transport domain such as HIV-1 Tat peptide, oligolysine or oligoarginine is covalently bonded to the N-terminal and/or C-terminal of a target protein.
Korean Patent No. 490362 discloses a complex wherein oligolysine is covalently bonded as a protein transducing domain to the N-terminal and/or C-terminal of a protein in order to improve cell transduction.
Through extensive research, including the above patents, it was found out that HIV-a Tat peptide, oligolysine, oligoarginine, oligo(lysine/arginine), PEP-1 peptide, and the like improve cellular transduction of proteins.
In addition, Korean Patent No. 787393 discloses an FK506 binding protein (FK506BP) fusion protein and a composition for improving atopic dermatitis and allergy comprising the same.
However, nothing is known about the use of FK506BP or FK506BP fusion protein for prevention or treatment of ophthalmic diseases.